president obama has said crossing that line would be a game changer. well, now critics are calling the country's credibility into question, while the white house still wants more evidence. nbc's tracie potts has details now from washington. tracie, good morning. >> reporter: hi, betty, good morning. and more from syria's state news agency this morning, its prime minister convoy was attacked in damascus. the prime minister said to be okay. varying reports of deaths and injuries from that attack. but it does underscore the seriousness of the violence there and why some here in washington want to act quickly. amateur video from syria, the fighting getting worse. and now the u.s. has some evidence syria's government may have used chemical weapons on its own people. president obama had called that a red line for action. now he's cautious. >> knowing that potentially chemical weapons have been used inside of syria doesn't tell us when they were used, how they were used. >> reporter: there's pressure from capitol hill to act, soon. >> for america to sit on th